I just bought a used NAD T514 CD/DVD player which I intend using as a transport for CDs & MP3s along with an external DAC. It sounds superb, even without a DAC, but when in PLAY mode, I can hear a ticking sound from the transport. Very annoying! Sounds just like a wall clock ... tick, tick, tick.

At first, I thought it might have been a crook belt or a cog gone bung; I've opened her up and the ticking sound seems to come from the encapsulated motor mechanism that slowly turns the gears that advance the laser across the surface of the CD.

Anyone else had a similar experience? Any suggestions on how I can quieten this device?

At worst, I intend replacing the entire transport mechanism. Would anyone know what part number to look for or a suitable replacement?

I guess the follow error possibilities:
1) the hole diameter of the cd is to large (respective the output diameter of the turntable is to little). In this case you don't get center lying of the cd itself and you can hear that you describe. Then you need a new motor pulley.
2) your disc motor shaft in their sintered bearings staggers to many. If this is present, your describted sound goes away if you put distance devices under your front feed of your cd player (crooked standing). Then you need a new disc motor
3) Your compact disc have to large height proposal (warped). In this case your describted sound comes from the laser lens (lens goes a long way up and down, focus servo buffer amp produce a large correction signal). This is good to observe by a full compact disc (one miniute before end - laser lens resp. collominator lens is good to see).
I hope, you understand my bad english language - I use the language tools by google.

Thanks for that info tiefbassuebertr - it took me a while to get my head around it but I think I understand.

I have had another close look at the laser mechanism in operation (while holding it in my hand). Three things: commercially bought CD's make a quieter clicking sound than home burned CD-R's; the repeating mechanical ticking sound gets faster as the laser moves towards the centre of the disk; lastly, it ticks only when in 'play' mode.

My guess is that the laser requires realignment as it is constantly having to correct itself.

The mechanism is marked as follows: DL3EG 6C04 512 623 72 060311SS B2

I believe it is a Samsung laser mechanism but I cannot find a replacement anywhere (unless I buy 500 or more).

I have attached photos.

I prefer not to fool around with the laser gain because the unit works perfectly (other than the ticking sound) and would not like to unnecessarily shorten its life. However, can the focus and fine tracking offset be adjusted on this critter? Anyone?

Many DVD based pickups/mechs are noisy due to the way the servos operate... something many notice.
Does it make the noise if you pause it, as that stops the sled ?
tbh it sounds as though it's normal for something like this.

Hard to say then, without actually hearing it for real. Ticking noise is characteristic of general servo noise (produced from the current in the tracking windings on the lens assembly).
The gears for the sled normally turn so slowly that I wouldn't expect that to be an issue, the motor usually just inches it's way around... again without actually seeing and hearing it's hard to make a judgement call.
Never the less in "pause" the servos are still active as the disc still rotates and the lens is still focused...
Could the sled motor be run off a pulse width modulated drive... as in some portable etc...

Just reading your "three comments" above. CDR's being more noisy does point to servo noise as the "data" is not as clearly defined. CDR's are fundamentally different to pressed discs which are reflective. On these a change in data 1 to 0, 0 to 1 occurs when ever there is a change from a "pit" to a "land" on the disc surface. The CDR just has reflective... non reflective, corresponding to where the ink has been "burned" during recording.
The upshot is the CDR gives a "poorer" waveform that the laser has to track.

If you have a disc with a defect does the noise get "worse"
Look at post #54 here. Try a bit of black ink or use some masking tape and paint a wedge on an old disc. Test CD for CD player adjustment

Just reading your "three comments" above. CDR's being more noisy does point to servo noise as the "data" is not as clearly defined. CDR's are fundamentally different to pressed discs which are reflective. On these a change in data 1 to 0, 0 to 1 occurs when ever there is a change from a "pit" to a "land" on the disc surface. The CDR just has reflective... non reflective, corresponding to where the ink has been "burned" during recording.
The upshot is the CDR gives a "poorer" waveform that the laser has to track.

Yes, but highly depend of the CDR type or/and the soft-and hardware for burning. The quality of the signal by the HF/RF testpoint indicates this clearly. If the difference regarded sharpness and level low compare to pressed CD, you have good quality.
The noise in play mode by DVD - and especially BD players is in general much more higher than by clean PCM CD players, also through the very high values of PRM.
I recommend to use for playing PCM CDs a clean compact disc player (NAD5320/5325 with Olympic laser head and Sanyo DAC is a good choise and cost-effective at the same time). Using of a DVD player I recommend only for Video-dvd's and MP3 coding compact discs.
To find out, whether your reported and unwanted effects is through a failure or naturally the best way is to buy a used DVD player model, where the same Samsung loader is inside (at best from Samsung itself). From there you get also a service manual. Then you can perform a explicit trouble shooting

Thanks to all for your comments. I will try the test disk referred to by Mooly and report back.

Meantime, you may be wondering why I am so keen to keep my NAD T514 player... Well, in short, it's a very good player! I like it a lot. I use it to listen to regular CD music as well as MP3's (which I sometimes have playing all day as background music). I have dedicated CD players from Marantz and Pioneer, plus a top-shelf player from Denon, plus others - and the NAD T514 holds its own very, very well.

I use my NAD mostly with an Electrocompaniet ECD-1 DAC, itself costing many times more than the NAD T514. But quite frankly, the NAD T514 benefits only very little from an external DAC - it's that good!

For any DIY'ers interested in learning more about CD/DVD laser alignment (along with a general explanation about how the laser mechanism works), here are two links that I found to be quite informative: